1. Field of the Invention
The present invention relates to a paging system control apparatus and, more specifically, to a paging system control apparatus which performs a queuing operation which arranges the call signals of randomly input calls into a prescribed transmission signal format.
2. Description of the Prior Art
Among the transmission signal formats of a call signal in conventional paging systems is a format arranged in accordance with the international standard signal scheme known as the POCSAG signal (CCIR Recommendation 584-1 (1982-1986), Standard Codes and Formats for International Radio Paging).
As shown in FIG. 1, the transmission signal format of the POCSAG signal scheme consists of a plurality of batches. Each batch is divided into 8 groups (group 0 to group 7), and each group is further divided into 2 code words (hereinafter referred to as CWs). Each of the 8 groups corresponds to the 3 least significant bits of an identity assigned to each pagers (i.e., 000=group 0, and 111=group 7), and all of the pagers used in a paging system are distributed to the 8 groups.
Call data input to a paging system control apparatus are converted to a call signal having a paging signal format. The call signal is constituted of an address CW of one CW when it does not include a character display (messages), and of an address CW of one CW and one or more message CWs that correspond to the length of the character message to be displayed. An arrangement is so constituted that the address CW is necessarily placed in the group corresponding to the 3 least significant bits of a pager's address in a call. The message CW(s) occupies the CW next to the address CW and, if necessary, CWs in subsequent group or groups accord with the length of the message.
To transmit a POCSAG signal as described above, the conventional paging system control apparatus has one queue buffer having a configuration as shown in FIG. 2, and stores the call signals of the randomly input calls in their sequence of arrival and sequentially transmits those in a cyclical manner. In FIG. 2, batch n and batch n+1 denote memory areas of the queue buffer corresponding to the nth and (n+1)th batches, respectively, and G0-G7 represent memory areas for the respective groups of each batch and have a memory capacity of 2 CWs.
The above-described conventional paging system control apparatus stores the call signals of input calls in the queue buffer while queuing those in their sequence of arrival. Therefore, when call signals are stored in the queue buffer, for instance, as shown in FIG. 3 (b), the control apparatus cannot accept, for queuing, a new call of group 2 as shown in FIG. 3(a) in spite of the existence of empty areas separated from each other, because there cannot be secured an empty area having the required contiguous length in the area for group 2. As shown in the example above, batches of a transmission signal format are not used efficiently in the conventional control apparatus. That is, a valuable radio resource is not used effectively.
Accordingly, an object of the present invention is to minimize empty areas of batches, i.e., to use the batches more efficiently.
Also, in the present invention, the reallocation operation is made relatively easier by employing two queue buffers having the same configuration and performing the reallocation operation between the two queue buffers. Further, the reallocation operation is performed on all of the call signals accommodated in the queue buffers to secure, in one operation, as large empty areas as possible for not only one new call that initiates the reallocation operation but also new calls that will occur subsequently.